Interferometric sensors may be used to measure a variety of different physical parameters. For instance, an interferometric sensor may be used with an optical fiber that is deployed through a region of interest. When light is launched into the fiber, the sensor (or reflector) returns backreflected optical radiation that then may be analyzed to determine variations in a parameter of interest, such as pressure, temperature, strain, etc. Such sensors have proven to be useful in a variety of applications, such as in oil production, to identify and determine a variety of downhole properties, such as pressure, vibration, temperature, fluid flow characteristics, etc.
An interferometric sensor may be deployed as a single point sensor, such as a sensor that is located at the end of an optical fiber. The returned light then provides information corresponding only to the location at which the sensor is positioned. In applications in which multiple data points are desired, a plurality of optical fibers may be deployed through the region of interest, each of which contain a discrete sensor. In such applications, separate interrogation and acquisition equipment arrangements are required for each fiber, thus increasing the cost and complexity of the overall system.
Interferometric sensors also may be arranged in an array of discrete sensors deployed at intervals along the length of the optical fiber. Acquisition of information from such arrays requires the ability to distinguish the returned light from each reflector. In certain types of arrays, the reflectors are wavelength encoded, meaning that each reflector responds to an interrogation pulse having a particular optical wavelength. In such a case, the returned light may be wavelength multiplexed in order to identify the particular reflector from which the returned signal was received. However, wavelength multiplexing schemes do not provide location information. Thus, in addition to any inherent imprecision in knowing the exact location of a reflector that corresponds to a particular wavelength, any ambiguity in the returned optical signals may make identification of the corresponding reflector difficult. Yet further, interrogation of such arrays requires that each reflector respond to a different wavelength, thus excluding the implementation of arrays of identical sensors. Thus, systems which implement wavelength multiplexing schemes may not be optimal for all applications.